The software for NASA’s Northstar Systems computed tomography (CT) and Picometrix Terahertz CT systems do not have the ability to unwrap and reslice cylindrical CT data to allow top-to-bottom, 2D sheet views of the data. Therefore, it is difficult to size flaws laterally (although viewing slices in the slice view plane allows sizing flaws in the depth [exterior-to-interior] direction). The unwrapped and resliced view would greatly facilitate inspection assessments.
The objective of this innovation was to develop the software to allow the unwrapping and reslicing of cylindrical CT data, and also provide a suite of image processing and analysis methods (including computerized flaw sizing) for the unwrapped/resliced images. Additionally, by writing the software, NASA Glenn can maintain the software and upgrade its future capability as custom needs arise.
The software method is applicable for analyzing cylindrical and partially cylindrical objects inspected using CT. This method involves unwrapping and reslicing data so that the CT data from the cylindrical object can be viewed as a 2D sheet in addition to a 3D volume rendering. By performing this transformation to a 2D sheet, visualization of the data is possible in one view without having to rotate the volume rendering. The method is based on interior and exterior surface edge detection, and under proper conditions is fully automated and requires no input from the user except proper voxel dimension from the CT experiment and wall thickness of the part.
For v2, significant upgrades have been performed. Overlay information is retained when image value is changed (both on top view slice and reslice image windows). A circle gauge allows the user to place, move, and resize a circle gauge on the MAIN top view slice and unwrap reslice windows in order to screen for critical flaw sizes. The Sub-Voxel measurement module was modified extensively. Line profile and line profile gradient displays are shown for lines drawn. Full-Width Half Max measurement, in addition to edge detection measurement, is now available to measure flaw lengths when a line is drawn across the flaw. Flaw angle measurements capability have been added.